1. Field of the Invention
The present invention relates to an optical reading head, particularly for reading luminescent code bars on documents and the like, which reading head is provided with a source of light for irradiating the bars and with a detector for collecting the rays emitted by the bars by means of an optical guide.
For a correct conversion of the code bars into electric signals it is essential that the bars are very sharply and distinctly observed by a light-sensitive detector. For this purpose it is desirable that the optical guide extends to the surface of the document, so that the small area of one code bar on the document can be observed with the least possible losses. This cannot be realized, because the irradiation of the area in question will then no longer be possible. For the sake of an even irradiation of the area the optical guide has to be positioned too far from the document, in consequence of which the area observed is enlarged and the quality of detection diminishes.
2. Description of Prior Art
In a known reading head the optical guide is formed by an optical fibre, and a separate optical fibre is utilized for transmitting light from the source of light to the code bars. This arrangement meets the difficulty of a source of light and a detector that are in each other's way, and thus, if no special measures are taken, they both have to be positioned as near as possible to the code bar to be read.
The solution according to the known reading head has the drawback that it requires a very intensive source of visible radiation, which develops much heat and, as a consequence, has to be cooled, and which has a short life, which increases the risk of operating trouble. Moreover, the ends of the optical guides always hinder one another near the document.